It is understood that any reference hereinafter to the 4L60 transmission also references the 4L60E and 700R4 transmissions, in that all 3 variations are functionally identical at the point of novelty of the instant invention, the crucial thrust bearing assembly of the rear planetary gear. The term “present bearing assembly” is also used interchangeably with “bearing mod” in that the present invention modifies the original OEM bearing configuration.
General Motors [GM] introduced the 4L60 automatic transmission back in 1981, and it is still being manufactured in upgraded format today. Early on, it displayed a problem with premature failure in the rear planetary. This failure could not generally be attributed to the otherwise-stable reaction carrier gears and housing. Rather, it became clear that the primary problem was due to rear thrust bearing failure, primarily from overheating.
GM made several attempts to correct this problem, about the same time that the 4L60E electronic upgrade mod was introduced in 1993. GM engineers apparently thought that they could resolve the overheating failure by simply improving the flow of lubrication [lube] into the bearing. More specifically, GM introduced a pattern of 4 cross-drilled lube pins on the back face of the rear planetary [FIG. 3] which were clearly designed to improve lube flow. They also mounted a lube shield on the back of the rear planetary in an effort to “catch” extraneous fluid and force it down into the 4 lube pins.
However, the bulk of 4L60 repairs in the time since then have demonstrated that GM's improved lube passages failed to cure the bearing's overheating problem—that is, the failure rate today is about the same as it was prior to the 4-pin mod. As a case in point, for one failed 4L60, the lubrication intended for the rear planetary [containing the present bearing mod] was completely shut down due to failure of the front planetary. In this extreme instance, the four outboard rear planetary gears actually melted from the resulting extreme heat—yet the larger new thrust bearing, centered between the melted gears, remained completely intact and functional. This confirms that the problem with the rear planetary thrust bearing is not how well it is being lubricated, but rather, how well it can dissipate heat.
The significance of this failure becomes even more remarkable when the scale of the following four observations is taken into account [see below]:    [1] The large range of GM vehicle platforms that have used and/or still use the 4L60/4L60E/700R4 transmission    [2] The large percentage of failures showing up at independent repair shops that can be directly attributed to the 4L60 planetary gear bearing    [3] The fact that this 4L60 failure has persisted for 20-odd years despite the apparent best efforts of GM engineers to improve rear planetary lubrication    [4] The present new 4L60 bearing mod, designed to cure this long-standing and wide-ranging problem, has held up under prolonged worst-case testing, without any wear[1] GM Platforms Using the 4L60 Transmission            Chevys with overdrive, including SS Impala, Caprice, Camaro, Corvette        Chevy and GMC SUVs, including Suburban, Tahoe, Blazer and Jimmy        Chevy and GMC Pickup Trucks, including the S10 1500/2500 series        Chevy and GMC Vans, including Astrovan and Yukon        Chevy and Pontiac Station Wagons[2] Survey Revealing Percentage of Failures Due to 4L60 Rear Planetary        
An informal survey of 30 randomly-selected independent transmission shops was conducted to get first-hand anecdotal data on the percentage of failures that veteran shops have experienced over the years. These repair shops are the critical juncture where failures of every type come pouring in. These shops were randomly selected, and only shops that qualified with at least 10 years experience were considered. They were also drawn from 22 different states to help account for variations in terrain and weather across the U.S. Each manager/rebuilder was asked, “when rebuilding the 4L60 transmission, in what percentage of these units must you install a rear planetary because the planetary failed?” Results of this poll confirmed the long-term problem:                Average failure rate due to rear planetary was 35% across all 30 shops        All responses fell in a range of 20-50%, after high/low were thrown out        Most shops responded with a range of values, most commonly 30-40%        Only 4 shops clocked their failure rate on the low side at 10% or 10-20%        As many as 9 shops in 7 different states clocked their failure rate on the high side at 50%        The inventor's shop has recorded a 40% failure rate, both before and after the 4-pin lubrication mod[3] 4L60 Planetary Failure Rate of 35% has Held Steady Over Time        
From these 30 transmission shops, the survey further confirmed that the failure rate due to the rear planetary has not changed much, if at all, in the last 20 years, including GM's transition from the original 4L60 to the electronic 4L60E, and including GM's lube flow mod which was aimed directly at this problem. This is a catastrophic failure rate, considering that the root cause is a relatively small and inexpensive rear thrust bearing.
[4] Present Bearing Mod Validated by Worst-Case Drag Racing Trials
A local racing enthusiast was experiencing repeated rear planetary failures in his 4L60, while trying to drag race down a ¼-mile track. To avoid these persistent costly teardowns, he turned to the present inventor to solve this nagging riddle. After considerable research and static testing, the present bearing mod prototype emerged. As a “trial-by-ordeal” validation across a prolonged period of time, the ¼-mile drag strip “hole shots” pose perhaps the toughest maximum-force, accelerated-wear tests possible for a new bearing assembly. This drag-racing 4L60, with prototype rear planetary bearing installed, has produced the following exemplary results across 1½ years without a single flaw or the slightest hint of trouble:                The car was a 1969 Pontiac Firebird, driven daily for a total of 12K miles        This 3600-lb street car generates 450 HP/500 ft-lbs torque @ the wheels, 560 HP/600 ft-lbs @ the flywheel        12 visits to the track across 1½ years, with 4-12 “hole shots” per visit, plus many additional trials with slicks        In addition, each drag race was preceded by one or more “burnouts” to tire seizure of 8-10 seconds each @5000 rpm        All of this tallies up to over 200 successful “hole shots” along with their 200+ associated “burnouts”        Best drag-race results: ¼-mile track @ 11.46 seconds/117.7 mph, ⅛-mile track @7.30 seconds/94.26 mph        After this severe abuse across 1½ years, this drag-racer transmission was removed and torn down for inspection [teardown was recorded]        Teardown inspection results: there was no visible or measurable wear on any surface or dimension of the prototype bearing        Hence, with no actual sign of wear after 200+ drag racing hole shots, the present bearing's time-to-failure has yet to be established        Moreover, since this was the 1st prototype bearing, all of this exemplary performance record was achieved without the incredibly durable Nickel Boron plating now being offered as a high-performance upgrade        
The apparatus and methodology embodying the present invention may be implemented in many different forms. Specific embodiments thereof will be shown in the following drawings and described in detail herein, with the understanding that the present disclosure is considered only an illustration of the principles of the invention. This description is not intended to limit the invention to the specific embodiments described and illustrated herein.